How to Optimize Fiber Orientation in Double-Curved UHPC Forms? Optimization Strategies and Performance Enhancement Solutions

Due to the complex bidirectional surface stress of double-curved UHPC shapes, fiber orientation directly affects the tensile strength, flexural strength, and overall stability of components, requiring scientific optimization to achieve precise matching between fibers and the stress direction of the curved surface. Drawing on its experience with the double-curved UHPC project at the Shanghai Astronomy Museum, Qinglong analyzes the core strategies and practical key points of fiber orientation optimization.

I. Stress Characteristics of Double-Curved Surfaces and Fiber Orientation Matching Principles

Precisely matching the stress direction is the core of fiber orientation optimization. Stress analysis basis: double-curved UHPC shapes mainly bear bending stress and shear stress, and stress concentration easily occurs where surface curvature changes, so fibers must be distributed along the principal stress direction; orientation matching principle: fibers should be preferentially distributed bidirectionally along the generatrices and parallels of the double-curved surface, with fiber content ≥60% in the main stress direction and ≤40% in the secondary direction, forming a three-dimensional mesh support structure; extreme curvature adaptation: for areas with a curvature radius ≤500mm, fibers must be densely arranged and aligned with the tangent direction of the surface to avoid fiber breakage during bending. Qinglong achieved stress balance in the double-curved project of the Ouargla Hotel in Algeria by following this principle.

II. Production Process Optimization for Precise Fiber Orientation

Fiber distribution is controlled through process improvements to enhance orientation precision. Spraying process optimization: high-pressure spraying technology is adopted, with nozzle angle and movement path adjusted to spray layer by layer along the double-curved surface contour, allowing fibers to naturally conform to the curved surface as the slurry flows; spraying pressure is controlled at 0.3-0.5MPa with movement speed ≤0.5m/s; mold design assistance: guide grooves are set on the mold surface to direct the slurry flow and indirectly control fiber orientation, with groove spacing ≤200mm and a depth of 3-5mm; vibration and compaction control: after spraying, a high-frequency vibrator (vibration frequency 2000-3000 times/minute) is used to gently vibrate the mold, promoting uniform fiber distribution and avoiding local clustering, while curved-surface-specific pressure rollers are used for compaction to ensure fibers bond tightly with the slurry.

III. Coordinated Optimization of Fiber Selection and Mix Ratio

Adapting fiber types and mix ratios strengthens the orientation effect. Fiber type selection: straight steel fibers or alkali-resistant glass fibers with a length of 12-20mm are preferred, offering better flexibility and tensile strength and facilitating orientation along the curved surface; chopped fiber dosage control: total dosage is controlled at 2%-3%, with oriented fibers in the main stress direction accounting for ≥70%; precise proportioning is achieved through layered addition. After Qinglong optimized the mix ratio, the flexural strength of double-curved UHPC increased by 35%; fiber surface treatment: fibers surface-treated with silane coupling agents are selected to improve bonding strength with the cement matrix, ensuring oriented fibers effectively transfer stress and avoiding debonding failure.

IV. Optimization Effect Testing and Quality Control

Optimization effects are verified through rigorous testing to guarantee component performance. Testing method application: X-ray diffractometers or industrial CT scanning are used to detect fiber orientation distribution and analyze the angle between fibers and the stress direction, with a qualification standard of angle ≤30°; sampling performance tests: each batch of double-curved components is sampled for flexural and tensile strength tests to ensure post-optimization strength improvement of ≥25% without significant performance fluctuation; production process monitoring: fiber orientation observation windows are set at key positions of the mold for real-time monitoring of the production process and timely adjustment of process parameters. Qinglong has established a full-process monitoring system, ensuring a fiber orientation pass rate above 98%.